our "person of the week." A name you likely haven't heard before, but someone who has already had a huge impact on our lives. Tonight, he's taking on a new and giant project. Our brains. Determined to make science sexy. At 6'4", he was the doctor standing a little taller than the president this week, during that big announcement at the white house. That the nation's leading scientists will now set out to map the hu where do you even begin? Well, that's the challenge, of course. Because the brain is probably the most complicated structure in the known universe. There are about 86 billion neurons in your brain and mine Reporter:86 billion neurons in one brain. A mind-numbing figure. This is a picture of a human brain. Reporter: And if anyone can help unlock that mystery, it's dr. Collins. Because he led the government's human gemone project, completing the first finished sequence of the human dna instruction book just a few years ago. Stephen colbert famously asked you about making science sexy again. Yes, he did. I thought you handled that well. Well, I do think science is enormously exciting right now. Reporter: Sexy? I would say! Reporter: It was not the journey he expected as that young boy, born on a sheep farm in virginia. He says he was given a gift from his mother -- curiosity. She home-schooled her son until the sixth grade. Did you think you'd be here, growing up on that farm? Last thing I ever would have imagined was being a scientist. Reporter: Mapping the brain. And mapping the brain. Reporter: And dr. Collins knows so many are waiting for that map. 100 million americans suffering from diseases that effect the brain right now. Parakinsson parakinsson's,al himzer's -- skets friend ya. A long list of conditions. Reporter: You heard the president say this at the white house. As humans, we can identify light years -- we have still not unlocked the mystery of the three pounds of matter that sits between our ears. I think he said it very well. It is amazing, three pounds? Reporter: More complicated than any computer and more colorful. Even as we sleep. A lot of people simply want to know why they had that dream last night or that nightmare. Well, we all have curiosity about the brain, don't we? It is our essence. And we have a chance to get answers to those questions. Reporter: Brainstorm. Brainstorm, I supposed. Hopefully brainstorm with a really nice outcome.

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